Information

© 2008 Microchip Technology Inc. DS39646C-page 281
PIC18F8722 FAMILY
22.0 COMPARATOR MODULE
The analog comparator module contains two
comparators that can be configured in a variety of
ways. The inputs can be selected from the analog
inputs multiplexed with pins RF3 through RF6, as well
as the on-chip voltage reference (see Section 23.0
“Comparator Voltage Reference Module”). The
digital outputs (normal or inverted) are available on
RF1 and RF2 and can also be read through the control
register.
The CMCON register (Register 22-1) selects the
comparator input and output configuration. Block
diagrams of the various comparator configurations are
shown in Figure 22-1.
REGISTER 22-1: CMCON: COMPARATOR MODULE CONTROL REGISTER
R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-1 R/W-1 R/W-1
C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0
bit 7 bit 0
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
bit 7 C2OUT: Comparator 2 Output bit
When C2INV =
0:
1 = C2 VIN+ > C2 VIN-
0 = C2 V
IN+ < C2 VIN-
When C2INV = 1:
1 = C2 VIN+ < C2 VIN-
0 = C2 V
IN+ > C2 VIN-
bit 6 C1OUT: Comparator 1 Output bit
When C1INV = 0:
1 = C1 VIN+ > C1 VIN-
0 = C1 V
IN+ < C1 VIN-
When C1INV = 1:
1 = C1 VIN+ < C1 VIN-
0 = C1 V
IN+ > C1 VIN-
bit 5 C2INV: Comparator 2 Output Inversion bit
1 = C2 output inverted
0 = C2 output not inverted
bit 4 C1INV: Comparator 1 Output Inversion bit
1 = C1 output inverted
0 = C1 output not inverted
bit 3 CIS: Comparator Input Switch bit
When CM2:CM0 =
110:
1 =C1 VIN- connects to RF5/AN10/CVREF
C2 VIN- connects to RF3/AN8
0 =C1 V
IN- connects to RF6/AN11
C2 V
IN- connects to RF4/AN9
bit 2-0 CM<2:0>: Comparator mode bits
Figure 22-1 shows the Comparator modes and the CM2:CM0 bit settings.